Vector quantinizer with distance measure calculated by using correlations

摘要

A vector quantizer for a speech coder for coding speech signals at low bit rates. The vector quantizer includes an auto- correlation calculation circuit for calculating an impulse response of a weighting function for each sub-interval of an input signal vector. The vector quantizer also includes a weighted cross-correlation calculation circuit for calculating a weighted cross-correlation of the weighted input signal vector and the weighted codevector having a code length equal to that of the input signal vector. The vector quantizer further includes a weighted auto- correlation calculation circuit for calculating an auto- correlation of the weighted codevectors, by using respective auto- correlations of the impulse responses, the codevectors and the cross- correlations. A distance between the input signal vector and the codevector is calculated by using the cross-correlations of the weighted input signal vector and the weighted codevectors, and the auto- correlation of the weighted codevector, and an index of a codevector corresponding to the minimum distance is obtained by an inspection circuit.